I found THE brownie recipe that checks all the boxes of fudgy, chewy, moist, firm, and similar to boxed brownie mix lol. It’s from King Arthur Flour and here it is! I followed it precisely, weighing instead of using cups, and I used Sonora wheat which means you can also use soft white! I found that when I weighed the sugar, I used about 1/2 C less than it called for (had I been measuring in cups). That was with organic cane sugar from Costco. I also loved that these brownies held together well, even when warm!
Another recipe worth mentioning: I am adding this recipe here because it’s quite good! But I have to admit, it’s not the type of fudgy brownie I prefer.
The recipe comes from Breadtopia and it uses khorasan/kamut wheat but feel free to play around with different grains (I tried it with spelt and didn’t like the texture).